Common stock (Detail)	9 Months Ended
	Sep. 30, 2022 shares
Class A [Member]
Class of Stock [Line Items]
Shares issued, beginning balance	665,901
Treasury shares, beginning balance	(48,788)
Shares outstanding, beginning balance	617,113
Conversions of Class A to Class B common stock	(12,093)
Conversions of Class A to Class B common stock, Outstanding	(12,093)
Treasury stock acquired	(6,818)
Shares issued, ending balance	653,808
Treasury shares, ending balance	(55,606)
Shares outstanding, ending balance	598,202
Class B [Member]
Class of Stock [Line Items]
Shares issued, beginning balance	1,488,292,852
Treasury shares, beginning balance	(197,818,349)
Shares outstanding, beginning balance	1,290,474,503
Conversions of Class A to Class B common stock	18,139,500
Conversions of Class A to Class B common stock, Outstanding	18,139,500
Treasury stock acquired	(6,850,133)
Shares issued, ending balance	1,506,432,352
Treasury shares, ending balance	(204,668,482)
Shares outstanding, ending balance	1,301,763,870